In general, a cartridge or blade unit of a safety razor has at least one blade with a cutting edge which is moved across the surface of the skin being shaved by means of a handle to which the cartridge is attached. Some shaving razors are provided with a spring biased cartridge that pivots relative to the handle to follow the contours of the skin during shaving. The cartridge may be mounted detachably on the handle to enable the cartridge to be replaced by a fresh cartridge when the blade sharpness has diminished to an unsatisfactory level, or it may be attached permanently to the handle with the intention that the entire razor be discarded when the blade or blades have become dulled.
Razor blade assemblies have been disclosed wherein cutting edge portions of the blade members are held between skin engaging surfaces which are generally referred to as the guard and cap of the razor blade assembly. The guard contacts the skin in front of the blade member(s) and the cap contacts the skin behind the blade member(s) during a shaving stroke. The cap and guard may aid in establishing the so-called “shaving geometry”, i.e., the parameters which determine the blade orientation and position relative to the skin during shaving, which in turn have a strong influence on the shaving performance and efficacy of the razor. The cap may comprise a water leachable shaving aid to reduce drag and improve comfort. The guard may be generally rigid, for example formed integrally with a frame or platform structure which provides a support for the blades. Guards may also comprise softer elastomeric materials to improve skin stretching.
In U.S. Pat. Nos. 4,586,255 and 4,378,634, the blade members are disclosed that are independently movable in response to forces encountered during the shaving operation by virtue of their being supported by spring finger biasing members integral with the body member, which exercise a bias against the blades during the shaving operation. In addition, mounting the blades on spring members, such as cantilever beams, may also be used to set the blade geometry by biasing the blades against a registration surface, such as clips.
In the construction wherein the blade support spring finger biasing members are formed integral with the body member, it is necessary to choose a material for the body member which demonstrates the proper qualities to provide a spring member, yet will demonstrate those qualities of durability necessary to provide a suitable housing for the blades, the cap and guard portion of the blade assembly. While plastic materials have been found which contain these particular qualities, regardless of the plastic which is used in the housing, when employed as a spring the material is susceptible to creep to a greater degree than that of a metal such as spring steel. However, metal or steel mechanisms increase cost and complexity of shaving cartridges.
Blades and blade support members are becoming thinner to provide for improved rinsing and cutting efficiency. However, thinner blades and blade support members have a tendency to move more during a shaving stroke, which may negatively impact shaving performance Accordingly, it is more difficult to sufficiently constrain the blades and/or blade support members, as well as prevent damage to the blades and/or blade support members during the process. In addition, the shaving forces may vary depending on the location of the particular blades and/or blade support members within the housing.
Thus, there is a need for a shaving razor cartridge having a simple and reliable design to sufficiently constrain the blades, and more particularly where the most force is applied during a shaving stroke. What is also needed is a method and design to constrain the blades and/or blade support members in relation to forces encountered during the shaving operation without damaging the blades and/or blade supports.